Java Utililty Methods Directory Copy nio

dest.mkdir();
for (File file : src.listFiles()) {
    if (file.isDirectory()) {
        copyDirectory(file, new File(dest, file.getName()));
    } else {
        copyFile(file, new File(dest, file.getName()));

if (src.isDirectory() && target.isDirectory()) {
    File[] files = src.listFiles();
    for (int i = 0; i < files.length; i++) {
        File targetFile = new File(target, files[i].getName());
        copyFile(files[i], targetFile);

copyDirectory(srcDir, destDir, null);

if (srcDir == null) {
    throw new NullPointerException("Source must not be null");
if (destDir == null) {
    throw new NullPointerException("Destination must not be null");
if (srcDir.exists() == false) {
    throw new FileNotFoundException("Source '" + srcDir + "' does not exist");
...

if (!destination.exists())
    destination.mkdirs();
for (File f : source.listFiles()) {
    final File target = new File(destination.getAbsolutePath() + "/" + f.getName());
    if (f.isFile())
        copyFile(f, target);
    else
        copyDirectory(f, target);
...

if (!sourceFile.isDirectory()) {
    throw new IllegalStateException("Source file should be a directory.");
if (!targetDir.getParentFile().exists()) {
    if (!targetDir.getParentFile().mkdirs()) {
        throw new IOException("Could not create " + targetDir.getParentFile().getAbsolutePath());
if (Files.isSymbolicLink(sourceFile.toPath())) {
    Path linkTarget = Files.readSymbolicLink(sourceFile.toPath());
    Files.createSymbolicLink(targetDir.toPath(), linkTarget);
    return;
if (!targetDir.exists()) {
    if (!targetDir.mkdir()) {
        throw new IOException("Could not create " + targetDir.getAbsolutePath());
for (String file : sourceFile.list()) {
    if (file.startsWith(".attach_pid")) {
        continue;
    File sf = new File(sourceFile, file);
    File newFile = new File(targetDir, file);
    if (sf.isDirectory()) {
        copyDirectory(sf, newFile);
    } else {
        Files.copy(sf.toPath(), newFile.toPath(), LinkOption.NOFOLLOW_LINKS);

if (srcDir == null || !srcDir.exists())
    return;
if (destDir == null || !destDir.exists())
    destDir.mkdirs();
final File[] srcFiles = srcDir.listFiles();
if (srcFiles == null) { 
    throw new IOException("Failed to list contents of " + srcDir);
if (destDir.exists()) {
    if (destDir.isDirectory() == false) {
        throw new IOException("Destination '" + destDir + "' exists but is not a directory");
} else {
    if (!destDir.mkdirs() && !destDir.isDirectory()) {
        throw new IOException("Destination '" + destDir + "' directory cannot be created");
if (destDir.canWrite() == false) {
    throw new IOException("Destination '" + destDir + "' cannot be written to");
for (final File srcFile : srcFiles) {
    final File dstFile = new File(destDir, srcFile.getName());
    if (srcFile.isDirectory()) {
        copyDirectory(srcFile, dstFile);
    } else {
        copyFile(srcFile, dstFile);

Preconditions.checkNotNull(source);
Preconditions.checkNotNull(destination);
Preconditions.checkArgument(Files.isDirectory(source));
Preconditions.checkArgument(Files.isDirectory(destination));
Preconditions.checkArgument(!source.equals(destination));
Preconditions.checkArgument(!destination.startsWith(source), "destination is child of source");
Files.walkFileTree(source, new SimpleFileVisitor<Path>() {
    final CopyOption[] copyOptions = new CopyOption[] { StandardCopyOption.COPY_ATTRIBUTES };
...

Preconditions.checkNotNull(source);
Preconditions.checkNotNull(destination);
Preconditions.checkArgument(Files.isDirectory(source), "Source is not a directory");
Preconditions.checkArgument(Files.isDirectory(destination), "Destination is not a directory");
Preconditions.checkArgument(!Files.isSameFile(source, destination), "Source and destination are the same");
Preconditions.checkArgument(!destination.toAbsolutePath().startsWith(source.toAbsolutePath()),
        "destination is child of source");
Files.walkFileTree(source, new SimpleFileVisitor<Path>() {
...

for (Path target : targets) {
    Files.walkFileTree(source, EnumSet.of(FileVisitOption.FOLLOW_LINKS), Integer.MAX_VALUE,
            new SimpleFileVisitor<Path>() {
                @Override
                public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs)
                        throws IOException {
                    Path targetdir = target.resolve(source.relativize(dir));
                    try {
...